Using the Porsche 997 and Ferrari F1 Brembo setuos as examples of drilled or slotted rotors being useless is highly misleading. For carbon ceramic setups like these, where the braking effect is almost entirely due to abrasive friction and the rotors and pads operate efficiently (and only efficiently) at very high temperatures, this is true. Also, these cars have efficient ducting to air to the rotors designed into their body work unlike the vast majority of cars on the road.
While the amount of outgassing from modern pad compounds is insignificant, the vast majority of cars run a iron rotor/non-ceramic pad combination and these work through both abrasive and adherent friction where there is a continual transfer of material from the pads to the rotors (this is why brake pads need bedding in, especially with a change in pad compound). With these, under heavy braking loads, the pad dust from the abrasive friction can prevent further transfer of pad material to the rotors, reducing the adherent friction component which lowers the overall braking power. Slots and holes give the dust somewhere to go, helping maintain the braking power in these extreme situations. Holes are better at passing the dust slots can fill and they also improve ventilation, reducing rotor temperatures, further maintaining braking efficiency under heavy loads and reducing pad taper although cracks can develop from the holes - this tendency can be greatly reduced with peening of the holes but no one does it as it would reduce rotor sales.
We are talking about braking at levels that shouldn't be experienced on public roads, even by manic heroes. For road use, normal ventilated rotors should be all that is necessary. And I seriously doubt that a properly driven and maintained Polo would experience pad or fluid fade with stock rotors except on a race track.
I fully agree about the confusion between braking sensitivity and power - the brakes on MkVI Golfs are too grabby yet people who don't have a clue think this is due to the brakes just being more powerful. If anyone knows the adaptation to reduce the sensitivity on a MkVI Golf, please pass on the info!
Scotty, come for a drive with me or let me take you for a drive in your car (do this before you judge me as being 'snooty' - getting this old has taught me a few things).
Last edited by kaanage; 24-03-2012 at 02:02 AM.
Resident grumpy old fart
VW - Metallic Paint, Radial Tyres, Laminated Windscreen, Electric Windows, VW Alloy Wheels, Variable Geometry Exhaust Driven Supercharger, Direct Unit Fuel Injection, Adiabatic Ignition, MacPherson Struts front, Torsion Beam rear, Coil Springs, Hydraulic Dampers, Front Anti-Roll Bar, Disc Brakes, Bosch ECU, ABS